Automatic navigating instrument for craft guidance



Dec. 2?, R949 J. HERBOLD 2,492,14

AUTOMATIC NAVIGATING INSTRUMENT FOR CRAFT GUIDANCE I Filed May. 13, 1947 s $heets-Sheet 1 CLOCK SELSYN GYROSYN COMPASS 26 lnvi'ntoi' 2 P Roma I H rbolci D62. 2?, 1949 R. J. HERBOLD 2A$2A4$ AUTOMATIC NAVIGATING INSTRUMENT FOR CRAFT GUIDANCE Filed May 13, 1947 v 6 Sheets-Sheet 2 Inventor Robe rk I. erbold Gnu-mu Dec. 2?, 1949 R, J, HERBQLD 2,492,148

AUTOMATIC NAVIGATING INSTRUMENT FOR CRAFT GUIDANCE Filed May 13, 1947 6 Sheets-Sheet I5 A I I 17g 172 1&6 173 Roberi I Herbold (mm-neg Summer Dec. 2'7, 1949 R. J. HERBOLD 2,492,148

AUTOMATIC NAVIGATING INSTRUMENT FOR CRAFT GUIDANCE Filed May 13, 1947 6 Sheets-Sheet 4 elahm a ll i 1 A g 1 c A RObC-ZYi: I. Herbold Cittorneg AUTOMATIC mwma'rma INSTRUMENT FOR CRAFT GUIDANCE Filed May 15, 1947 R. J. HERBOLD 6 Sheets-Sheet 5 GQ Q 5) attorney HERBOLD AUTOMATIC NAVIGATING INSTRUMENT FOR CRAFT GUIDANCE Filed May 13, 1947' 6 Sheet 6 LONGTU DE 1 ELSY SWITCH ROL LATITUDE SELSYN LONGnlTU SELSY 155 AIQGENERA Robefl 3i Herboldi Patented Dec. 2?, i949 SATES UNITE AUTOMATIC NAVIGATING INSTRUMENT FOR CRAFT GUIDANCE Robert J. Herbold, Denver, 0010., assignor to Lafayette M. Hughes, Denver, 0010.

21 Claims.

This invention relates to an automatic navigation instrument and more particularly to a device which indicates the latitude and longitude of a moving craft and may serve for the automatic guidance of the craft according to a plotted course.

In my copending application, Serial No. 735,030, filed March 15, 1947, I have described an instrument for automatically guiding a craft relative to a course plotted on a chart simulating a segment of the earth which is moved in a timed relation with the apparent movement of a celestial body on which a fix is maintained, and wherein a course follower is moved automatically relative to the course by a light seeking electronic device, so that latitude and longitude determinations of craft position are indicated on the moving chart and the craft is guided accordingly.

A primary object of this invention is to provide a simplified construction in which the charted course is suitably located on the craft at a point remote from the light pick up device.

A further object is to provide such a construction in which the chart is stationary and a course follower is movable relative thereto by a remote control mechanism governed by the electronic light pick up device which maintains a celestial fix.

A further object is to provide such a device in which the latitude and longitude of points on a course may be plotted in rectangular coordinates on any desired scale and wherein the course follower is moved according to that scale so as to give an instantaneous indication of craft position.

A further object is to provide electrically synchronized mechanism governed by an angularly movable, fix maintaining, electronic device, which moves the course follower relative to the charted course in accordance with difierences in the angular positions of the electronic device caused by the craft movement.

In accordance with my invention, an astronomical fix is maintained by means of photo sensitive elements arranged to be moved automatically by their activation into a proper alignment with a light ray from a celestial body. Compensation is made for the apparent east to west motion of the celestial body as caused by the rotation of the earth and any variation from that apparent motion as is ascertained by the light pick up device is communicated through synchronized mechanism to a course follower which is moved automatically over the plotted course in correspondence with the craft movement. Latitude is determined by the inclination angle relative to a horizontal line of the axis about which the light pick up device revolves while maintaining its fix. Longitude is determined by the angle between the direction towards which the pick up device points at the instant position relative to its imaginary direction of pointing at zero longitude at the same time. The latitude and longitude of that course are preferably plotted on a flat surface in rectangular coordinates on any desired scale so that the movement of the course follower is proportional to the angular deviation of the light pick up device as caused by the craft movement. The course follower and chart which give a visual indication of craft position are also so constructed that the craft rudder may be controlled automatically by any deviation of the course follower from the path plotted on the chart.

Referring to the drawings which illustrate a preferred embodiment of this invention:

Fig. l is a vertical elevation. partly in section, showing the light pick up device and associated mechanism;

Fig. 2 is a top plan view of the chart and a course follower movable thereover;

Fig. 3 is a side elevation of the chart;

Fig. 4 is an enlarged detail of a course follower employed for visual indication of the craft position;

Fig. 5 is a plan view of the under side of the chart board;

Fig. 6 is a section taken on the line 8-8 of Fig.

Fig. 7 is an enlarged sectional detail of the pilot tube and the electronic pick up cells of Fig. 1;

Fig. 8 is a section taken on the line 8-8 of Fig. 7;

Fig. 9 is a sectional detail of the course follower shown in Fig. 2;

Fig. 10 is an elevation of a Selsyn generator motor unit that controls the position of the course follower;

Fig. 11 is a section taken on the line il-ll of Fig. 10;

Fig. 12 is a wiring diagram of the electronic circuits associated with the light pick up device;

Fig. 13 is the wiring diagram of the Selsyn motor controls which interpret the position of the light pick up device as latitude and longitude of craft position and govern the position of the course follower accordingly; and

Fig. 14 shows the wiring diagram of the electrical apparatus that controls the craft rudder as determined by the position of the course follower relative to a course plotted on the chart.

Device for maintaining a celestial fix This apparatus comprises, as shown in Fig. 1, a light seeking device or pilot tube It which maintains a fix on a celestial body, such as the sun or a star or a group of stars, during the apparent east to west movement thereof as caused by the earth's rotation. In order that the light seeking device may be universally or equatorially mounted for maintaining that fix, it is carried on a supporting tube II which is mounted for a limited pivotal movement on a shaft l2 that swings the tube about the shaft axis. This shaft is rotatably mounted within suitable bearings carried by a tubular casing l3 which has axially aligned projecting trunnion supports I4 arranged at right angles to the shaft axis. According to the position of the parts shown in Fig. 1, the center line of the device It is at right angles to the axis of the shaft l2, and the trunnion axis is at right angles to the latter. The trunnions are supported by a yoke I! which is held in a vertical position so that the light seeking device it may point to any portion of the sky and follow the apparent path of the celestial body.

' The yoke arms ii are carried on a support it that is stabilized by means of a suitable electrically driven gyroscope i1 and a weight it, so that the motion of the light seeking device It may not be aflected by any rolling or I The vertical rod is, which supports the base It of the yoke, is carried on a pin 20 mounted at its ends on a gimbal ring 2| pivoted on axially aligned trunnions on a supporting yoke frame 22. The latter is mounted on a turn table 23 which is arranged to be oriented so that the rocking trunnion axis is east and west and the shaft l2 may be tilted in a north and south plane. This is accomplished by means of a Selsyn or servomotor 24 controlled by a Selsyn generator 25 whose orientation is determined by a gyrosyn compass 2| or other suitable device. The shaft of motor 24 has a worm meshing with the worm gear 21 on the periphery of the turn table. Ball bearings 2! supporting the table and a center pin 29 projecting from the supporting table serve as a mount that permits the table to turn about a central vertical axis aligned with the axis of shaft l9. Various motor constructions commonly controlled by means of a gyrosyn compass may be used to hold the frame 22 oriented. I

A suitable servo reversible D. C. motor 30, which is controlled by the light pick up device, is mounted on the yoke l and rotatably connected through bevel gears 3| with the shaft 32 that is pivotally supported in the yoke arms l5 and pinned to the trunnions l4. Any variation in the latitude position of the craft causes this motor 30 to rock the shaft l2 in its north and south plane and thus compensate for the latitude change in craft position and maintain the celestial fix. The light pick up device I is revolved about the axis of shaft l2 by means of the longitude motor 35. This motor is mounted on the under side of a swinging frame 36 secured to the casing l3 and trunnion supports l4. The shaft of motor 35 passing upwardlythrough the support 36 is connected through a gear 31 with a spur gear 30 keyed to the shaft l2.

Adjustment for declination of the sun is made by pivoting the support ll so as to swing the light seeking device III to a position of 23.5 either side of a perpendicular to the axis of shaft l2. This pivotal mount comprises a pin 40 carried by the shaft l2 and on which the tubular support II is rotatably mounted. A scale 44 fixed on the side of the shaft i2 is marked with degrees up to 23.5" each side of a central zero position. It is associated with a pointer 45 fixed on the support II, and the parts are so arranged that the light seeking device It may be angularly adjusted in ac- .cordance with the declination of the sun or other celestial body for the particular day of the craft movement. A vernier scale may be used. The support II is held in position by the two pitching of the craft.

screw threaded rods 4' plvotally secured to the member H on opposite sides of the pin 40. These screw members pass upwardly through slots in a cross bar 48 secured on the top of the shaft 02, and the nuts 49 hearing on the cross bar may be adjusted to tilt the light seeking device according to the declination as determined by astronomical tables. Thus, if the gyrosyn compass 26 holds the axis of the aligned trunnion bearings l4 in an east and west position, then the shaft l2 may be tilted to that angle from the horizontal which makes its axis parallel with the earth's axis.

' Hence revolution of the support ll about that tilted axis, after an adjustment is made for declination. causes the light device ill to follow the celestial body movement.

An indication of the craft position as to latitudeand longitude may be given by the latitude dial 52 and the longitude dial 53 by means of a latitude Selsyn generator 54' and a longitude Selsyn generator II and their associated synchronized motors as will be described. Avariation in latitude, which is reflected in the tilting of the shaft l2 as required to maintain a. celestial fix, may be communicated to the latitude Selsyn generator 54 through bevel gears 56 connecting with the bearing shaft 51 that is pinned to the left hand trunnion l4 and is mounted in the yoke arm. The longitude Selsyn 55 has its rotor shaft geared at 58 to the gear 38 keyed to the rotatable shaft l2. The Selsyn 55 is mounted on the under side of the rocking base 36. The latitude Selsyn i4 is carried on the side of the yoke l5.

Electronic control of light pick-up device The light pick-up pflot tube (Figs. 7 and 8) it has a small aperture 60 at its outer end through which a ray of light from the sun or star may enter. A suitable optical system may also be used to gather and condense the light. This ray of light is intended to activate one or two of the four cathodes, GI, 62, 63 and 64 of a multiplex photocell located within the tube which has a common anode 65. The cathodes are preferably flat plates of suitable light activated material which are so arranged reversely .in the four quadrants north, south, east and west that light coming from the north side of the axial line of the tube will strike the north cathode plate 6| and east light will strike the east cathode plate 62, and west and south lights will activate the other plates 64 and 63. These plates are spaced from one another and to provide a nonsensitive space therebetween. An opaque disk 66 is suitably mounted centrally of the tube above that space between the cathode plates, so that if the light ray is exactly central it will strike only the disk and no one of the cathodes; but if the light ray moves slightly to one side at a small angle, then it will strike one of the plates and activate the same. This photocell may be photo conductive, voltaic or emissive. It may be a photo emissive caesium oxide cell of standard construction protected by a glass envelope 61 and having the usual contact prongs projecting into a hollow base 68 carried on the tube LI and provided with the required electric contacts as will be understood.

Referring to Fig. 12 showing a diagram of the wiring related to the electronic light pick-up, the south cathode 6|, activated by light from a southerly angle, is connected through an amplifler I0 and associated battery circuit of standard construction with the anode 65. Similarly, the north light activated cathode 63 and anode GI a movable contact arm 18 adapted to make a' contact with one or the other of two terminals of the north and south latitude reversible D. 0. motor 30 (Fig. 1) which swings the latitude adjusting shaft l2. Similarly; the east and west amplifier systems 12 and 13 are connected to the coils of a relay 18 which controls the east and west longitude reversible D. C. motor 85 that rotates the shaft '|2.- Each of these motors 30 and 35 is connectedin a suitable D. C. circuit, such asmne providing 24 volts. Hence, a reversal of the associated relay causes a reversal of direction of rotation of themotor.

.Thus, if the sunlight, for example, enters the light tube It) and strikes only the south cathode 6|, it causes the reversible latitude motor 30 to move in such a direction as to swing the tube toward the south and to a centralizing position for the sun ray. If the sunlight hits the opposite cathode 63, then the motor is rotated in the craft is standing still or moving, since the motors are operated solely in accordance with the direction of the light, and the rotation of the earth or the craft movement does not interfere with the light pick-up. The opaque disk 66 ismade the same size as the image of the light ray so that a slight deviation of the light will activate one of the cathodes.

In order to bring the. light tube Ill initially into alignment with the sun rays from any po sition, I provide a suitable electrical hunting mechanism. A preferred construction comprises the four photoemissive cells 8t, 8t, 82 and 83 of standard type arranged outside of and around the pilot tube and 90 apart. See Figs. 7 and 8. These cells are separated from one another by the arcuate opaque light shields 88 which are so arranged that each tube is free to receive light mainly from a sector having a horizontal angle of less than 180, so that east light, for example, will affect primarily the cathode of ,the east tube 8i while northeast light will strike the north and east tubes 80 and 8| but not the others. An annular shield 85 located above the cells and around the tube serves to prevent activation of the outside photocells when light enters the tube aperture 60 and activates the interior photocells. Thus the inner cells take over the control when the hunting action aligns the tube with the sun.

These outer hunting cells B0, 8!, 82 and 83 connect respectively through suitable amplifying apparatus 84, 85, 86 and 81 with the coils of the two double throw single pole relays 88- and 87 with the photo tubes 8! and 83 "which receive the east and west lights.

These light hunting cell circuits are connected with the two motors 30 and 85 that are actuated by the cells within the pilot tube M. That is, the relay 89 of the. east and west hunting system govems the longitude motor that rotates shaft i2 and swings the arm ll, so that a north and east light activation of the hunting device swings the pilot tube to in an easterly direction by energizing the longitude motor 35. The other hunting system activated by the north and south light is connected with the latitude motor 30 so that it swings the shaft H in a north and south plane to make a latitude variation. Thus the activation of north and east cells causes both motors to swing the tube to the northeast. The hunting photocells outside of the pilot tube It! will therefore serve to pull the light tube over to a position where the flange above the tubes cuts of! the light, at which time the light will enter tube in and strike the inner cells. After the inner cells take control of the pilot tube, then the extraneous light striking the outside cells is immaterial. If desired, various other shield and cell arrangements may be provided to attain the proper hunting and control action. The photocells inside of the tube In do not take control of the movement of the pilot tube until they are activated by a direct ray of sunlight; and the amplifiers are regulated in accordance with the desired light intensity for proper operation of the relays.

charted course and follower equal angles between radial lines from the earth's center. Hence, on the chart I00 shown in Fig.2, the earth's equator may 'be represented by a straight line l0! and the Greenwich meridian of zero longitude by another straight line I02 at,

right angles to the first and intersecting it at the center of the chart or at any other desired point.

The line we may be located wherever desired,"

Africa. The line I04 represents .a course going east from Philadelphia to the same destination,

where the line I02 is the Greenwich meridian. The line I03 or other straight line, drawn on this chart is a rhumb line.

Since the chart may be made any convenient size, it may relate only to a desired small portion of the earth's surface so as to provide the maximum size of charted course that is permissible. There is no critical scale. A chart that is several feet in length could provide a plotted course from New York to Denver of very great accuracy, for example.

It will be observed that the vertical lines on the drawing correspond with longitude lines of the earth and that if one wished to travel north from any given position, his course would be indicated by a north or vertical line. Hence,

. of the course follower.

7 the North and South Poles are represented by the top and bottom horizontal lines of the chart. Thus, a square near the North Pole line may represent only a short distance, but the latitude and longitude angles are equal to those near the equator. This type of chart makes it possible to plot the locations of two points quite accurately, depending upon the size of the chart; and that may be as large as is required for the purpose. A given course line is plotted according to latitude and longitude angles, and this makes possible the plotting of a given course with any desired variations down to the shortest distance or a great circle course.

The angular variations that are reported by the latitude and longitude Selsyn generators 54 and 55 may be employed to move a course follower or a spot of light over the chart to indicate the craft position. For example, the follower I05 (Fig. 2) may be moved, bodily by Selsyn motors synchronized angularly with the Selsyn generators and arranged to translate the angular movement of the pilot tube I as linear movement of the follower or indicator relative to the chart.

The chart construction, shown particularly in Figs. 2 to 6, comprises a rectangular frame I06 carrying the horizontal flat chart board I00 on which the latitude and longitude may be suitably plotted. This frame has two opposed dovetailed slideways I01 (Fig. 6) parallel with the latitude lines; and two opposite slide members I08 and I09 have Vs interfitted with the slideways. These slide members I08 and I09 are connected together by a bridge structure formed of two parallel round rods IIO which are located above the chart. These rods are fixed in the tops of two spaced vertical arms III and H2 which are respectively secured to the slide members I08 and I08.

The course follower may be a plate II (Fig. 4) mounted to slide on the rods H0, which is provided with a central opening IIS and a suitable scale mark which aids in reading the latitude scale marked on'one of the slide rods I I0. Cross hairs II'I within the opening II8 serve for indicating both latitude and longitude. This course follower is a visual indicator permitting a pilot or navigator to ascertain the latitude and longitude of his craft position by inspection of the position If the craft is to be guided automatically to follow a plotted course then the follower I05 of Fig, 2 may be constructed as shown in Fig..9 and hereinafter described.

The course follower is moved over the chart by moving the slide bars IIO toward the left or' right (Fig. 2) and by moving the follower along the slide bars, This may be accomplished by motors controlled by the Selsyn generator motor sets and suitable mechanical devices. As shown, the movement of the course follower I 05 along the slide rods I I0 is governed by the Selsyn motor I20 (Figs. 2 and 13) which is mounted on the platform I23 projecting laterally from the upright III and itsassociated slide member I08. The Selsyn motor I20 is synchronized angularly with the latitude Selsyn generator 54 (Fig. 1), and the Selsyn set in turn controls the operation of a power or servo reversible D. C. motor I22 mounted on the platform I23. The Selsyn motor I20 reflects accurately an angular movement of the generator 54 that responds to any tilting of the shaft I2 of the light pick-up mechanism. If the gears 56 (Fig. 1) have a 1-1 ratio, then when the shaft I2 is tilted through the Selsyn generator 54 isgiven that same 10 angular movement. and this is transmitted to the Selsyn motor I of Figs. 2 and 10. A different gear ratio may be employed to multiply that angular tilt. The D. C. motor I22, which is driven by a suitable battery, transmits this angular variation to the course follower I05 by means of a drum I24 fixed on the end of the shaft of the servomotor I22. (Figs. 2, 3 and 10.) A cord I25 has its two ends secured to and wrapped around the two halves of the drum I24 so that rotation of the drum will move the cord in one direction or the other. A pulley I20 (Fig. 2) mounted on the opposite upright I I2 is 50 located that the cord I25 passes around the same. This cord is adjustably clamped to the courser I05 by means of a set screw I2I as shown particularly in Fig. 4. This adjustment permits setting the courser in a correct latitude and longitude position as determined by nautical tables. Since the chart may be made of any desired size, the distance through which the courser moves may be adjusted by varying the gear'ratio of the gears 56 of Fig. 1 or preferably by changing the diameter of the winding drum.

Selsyn controls The Selsyn motor I20 operates a suitable delicate switch mechanism which controls the power to the reversible D.'C. motor I22 from a suitable battery I30. The motor I22 has a permanent magnet field. The shaft of the servomotor I22 (Figs. 10, 11 and 13) carries two slip rings I3I, which connect the motor with two laterally projecting pairs of spring arm contacts 'I33and a pair of contacts I34 arranged radially' on the arm I35 carried on the end of the winding drum I24; Each of the spring contacts I33 is arranged to be struck by one of two central contacts I36 suitably carried on opposite sides of the arm I38 projecting radially from the shaft of the Selsyn motor I20. The arm I38 also carries two contacts I 38 arranged to strike one of the con tacts I34. The slip rings I3'I on the Selsynmotor shaft connect the battery with the contacts I31 and I39 on the arm I38. The two inner spring contacts I34 on arm I35 are so located as to be struck by a central contact I39 on the Selsyn arm I38 to complete the circuit when the upper contact I33 is struck by the member I 35. The contacts I33 have resistances I42 in their circuits so arranged that when the shaft of the Selsyn motor I20 rotates through aslight angle to cause the contact I36 to strike a contact I33, one of the resistances I42 is interposed in the circuit to provide a slow starting and stopping .speed. If the motor I 20- moves rapidly or through a greater angle, one of the spring held contacts I33 moves over to strike an outer contact I43 mounted on the arm I35 back of the spring I33 and which is connected to short circuit the resistance I42 and cause the motor I22 to move more quickly. The construction is so arranged that the reversible motor I22 is rotated in such a direction, depending on which way the Selsyn motor rotates, as to move the courser I05 to indicate the change in latitude. This direction of courser movement also depends on the direction of winding the cord I25 on the periphery of the drum I24. The wiring circuits are such that if the Selsyn arm swings to the left (Fig. 11) it progressively makes the contacts which rotates the motor I22 in a given direction, and reversal in direction of the Selsyn rotor reverses the motor I22. As soon as the I22 motor starts, it releases the contacts and again breaks the aeeaiee the Selsyn motor.

The Selsyn generator and synchronous motor set may be made in accordance with standard practice. The generator and motor of the latitude determining set are identical in construction, and comprise stators I50 and II like. a three phase induction motor. The rotors I52 and I53 each have a bobbin type of core provided with a single winding which is energized from a single phase source of alternating current. As shown in Fig. 13, the two rotors are connected in parallel with a source of alternating current conducted through suitable slip rings. The corresponding taps of the Y -windlngs of the two stators, are connected together. The altemating current for the rotors may be derived from the battery I30 which drives a D. C. motor A. C. generator set I55. The battery and the motor generator set may be connected with the Selsyn set through suitable switches and relays, as illustrated. In its operation, the rotor I52 of the latitude Selsyn generator 54 provides an alternating field cutting the windings of the stator I50 and thereby inducing a secondary current in that winding. This sets up a corresponding field polarity in the stator I5I of the Selsyn receiver I20 and the rotor I53 of the receiver has an induced field which is the same as that of the transmitter I52. Hence the rotor I53 of the synchronous motor will tend to stand at the same angle relative to its stator as does the rotor I52 of the generator set, and since the E. M. F. that is induced in each winding is equal, there is no circulatory current. If, however, the rotor of the transmitter is turned through a given angle, there will be a phase displacement between the E. M. F. induced in the transmitter and that in the receiver stator, and the resultant circulatory current between the two stator windings will pull the rotor of the receiving set to the same angular position as that of the rotor in the transmitter set. Hence any angular displacement of the latitude Selsyn 50 will be transmitted to suitably connected receiver Selsyn motors. 'The latter are located in any convenient position as required by the dial and chart mechanisms.

Latitude determination a sideral fix, and to do this the axis of the shaft I2 must be parallel with the earth axis. That is, the axis of the shaft is tilted at that angle to a horizontal line which corresponds with the latitude of the craft. When the craft is at the equator, the shaft I2.is horizontal and at the North Pole the shaft is vertical. Hence, if a craft flies from the equator to the North Pole, the shaft will move through 90 from a horizontal to a vertical position.

The Selsyn motor I20 of Fig. 2 is synchronized as above explained with the Selsyn generator 54. Hence, as the shaft I 2 is tilted, the gears 56 transmit this angular motion to the Selsyn generator 54 and the shaft of the Selsyn motor I20 has its shaft turned through the same angle. This rotation of the shaft'of the Selsyn motor I20 causes the motor I22 to be energized and to wind the cable I25 and move the courser I05 in accordance with that change in angular position. The periphery of the drum I24 and the angular movement of the motor I22 are coordinated so that the movement of the courser I05 across the plotted angles of latitude on the chart correspond with the angular tilt of the shaft I2. As above stated, the chart may be plotted on any desired scale and adjustment made therefor in the winding drum circumference or in the ratio of the gears ;56. Other types of control may be employed and to insure that the courser I 05 is mov% to the required distance and in accordance with the scale of the chart to indicate the angle through which the shaft I2 is tilted.

Longitude determination Longitude is determined by comparing the observed angular position or pointing direction of the arm II (Fig. 1) which carries the light seeking tube I0 relative to the imaginary direction of pointing of a similar device located on the Greenwich or other meridian from which longitude is determined. This is readily accomplished by employing a chronometer which is set to run on Greenwich time and by comparing that time with the actual time where the craft is located as determined by the east and west angular position of the support II. Philadelphia is located at approximately 75" west longitude and a clock there will show a time that is 5 hours earlier than that of Greenwich. The longitude of craft position at any time may be ascertained by means of a difi'erential Selsyn unit having its stator governed by the clock and its rotor governed by the longitude Selsyn generator 55. Hence the clock I60 (Fig. 13) having Greenwich or other selected time is employed to rotate synchronously the rotor I6I of a Selsyn motor having a stator I64. Likewise, the Selsyn generator 55 controlled bythe pilot tube angular position (Fig. -1) may be used to drive the rotor I66 of another Selsyn motor at its rate. The stators govern an auxiliary differential Selsyn unit I62 in which both stator I63 and the rotor I 65 have three phase windings. The stator I63 has a Y-connection with the stator I68 of the Selsyn unit driven by the clock. The three phase winding I65 of the rotor of the differential Selsyn has its terminals similarly connected with the stator of the Selsyn generator 55 that is controlled by the pilot tube. The rotor I66 oi the unit 55 is connected in parallel with the source of alternating current which energizes the rotor I6! of the clock driven unit, and with the connections so arranged that the two rotors tend to turn in such directions that the difierential Selsyn I62 gives the algebraic sum of the angular positions of the two controlling rotors I6I and I66 and its rotor I65 gives the longitude angle of the craft. This resultant displacement of the rotor I65 may be employed to control the movement of the slide I I0 that carries the courser (Fig. 2) or the angular position of the rotor I65 may be read directly on the longitude dial 53 mechanically connected to the rotor, with the aid of a Vernier.

The auxiliary Selsyn unit I62 which carries the three phase rotor winding I65 is connected through a suitable switch control, such as is shown in Figs. 10 and 11, to control a suitable reversible D. C. motor I68 which in turn operates a winding drum I69. (Figs. 3 and 5.) This auxiliary Selsyn differential I62 and the driving motor I68 are suitably mounted on the under side of the chart board. A cable I10 has its two to its start, if the longitude is known; and in that case the Selsyn clock will be set to the exact solar time at that position of longitude so that the rotor I85 of the differential Selsyn will stand at the same angle as that of the rotor IGI ofv the clock Selsyn and of the rotor I88 of the longitude Selsyn 55 governed by the pilot tube 60. Then when the craft moves east or west, the two control Selsyns will get out of step and the angular difference will be shown by the differential Selsyn rotor. The size of the winding drum is proportioned in accordance with the size of the longitude scale on the chart to insure that the course follower is moved across the scale in an exact angular relationship to the craft movement relative to the earth longitude. The latitude and longitude measurements are also shown on standard dials provided with verniers that are observable by the pilot or navigator of the craft. These rotatable dials of these units 52 and 53 (Fig. l) are directly connected to the shafts of the Selsyn receiver rotors II and N5 respectively. Hence the pilot has a direct vision indication of craft position as regards latitude and longitude. This aspect of my construction makes it possible for the transmission of this position intelligence to any part of the craft.

Craft guidance mechanism In so far as above explained, the mechanism may be used for the guidance of a pilot or navigator who manually controls the craft. This apparatus is, however, constructed to control the guidance of the craft automatically, such as where one or more rudders of the craft may be operated electrically under the control of the reversible D. C. electric motor I80, Fig. 14. This motor is preferably connected through a Selsyn or servomotor system which governs the powerful motor capable of operating and holding the craft rudder in a desired position, as will be understood. The rudder is controlled to move through a pre-determined arc to such a position that the craft is slowly brought on course if it has deviated therefrom. This control is effected by an electronic apparatus, as shown primarily in Fig. 14, in which a spot of light I85 is projected by the courser I05 onto the chart at the exact point which indicates the craft position. This spot of light is employed to govern further electronic apparatus controlling the rudder which is so arranged that if the craft deviates from a plotted course it will be automatically returned to its direct line of travel. This is accomplished without computation of latitude and longitude and without actual knowledge of the crafts position at anyinstant.

For the automatic guidance of the craft, the

'chart is provided with two surfaces I82 and I83 immediatelyadjacent to the plotted line I04 which have different light'reflective characteristics. The courser is provided with a self-contained illuminating system which throws a spot of light I85 onto one of'the surfaces of the chart I00. The surface I82 may be a removable strip of material of medium or low light reflectivity but not of full light absorption, such as a matte surface on metal. The other removable strip I83 has a mirror surface or one of high reflectivity, such as may be made of polished metal. The mirror surface 188 may reflect about twice as much light as does the matte surface I82. These two strips serve to govern electronic apparatus which is activated differentially by the different light intensities reflected by the two surfaces. The line I04 between these two surfaces opaque casing or light shield I88 shaped as a frustum of a cone. An internal annular shield I89 confines the light rays in the ring shaped space between the shields. A suitable lens and diaphragm system I90 condenses the light from these bulbs and focuses it as a fine point of light I85 on the surface of the chart I00. That light spot strikes the chart at the exact point which indicates the craft position, and it serves as a visual indication of the craft position if so desired by the pilot. For his convenience, the courser may be arranged to travel beneath a transparent chart surface so that the spot of light shows through. However, this aspect of the invention is intended for the automatic control of the craft and no one needs to see the light ray.

This light spot I85 controls electronic appa- I ratus by being reflected back through a condenser lens I92 arranged within the tube I89 and the light thus collected is thrown onto the cathode I94 or sensitized surface of a suitable photo cell mounted inside of that tube I89. As indicated diagrammatically in Fig. 14, the cathode and a suitable anode I85 are connected through a suitable amplifier I96 and associated battery system which is arranged to operate a double relay system that controls the direction of rotation of the reversible direct current electric motor I that either governs the rudders directly or controls a further motor which controls the lateral guidance of the craft.

Various control systems may be employed for that purpose; but the one illustrated in Fig. 14 comprises a relay I91 which is actuated by the light spot I striking the lesser reflective light surface I82. The other relay I88 is governed by the movement of the light spot to the more highly reflected surface I83. Each relay has its contact arm resting in an open position when the light .spot I85 strikes only the black course line I04,

which has such a high absorption that not enough light is reflected back to activate the selected photocell. The spring I99 which holds the contact arm of relay I87 open is so adjusted that it closes when the light spot I85 moves to illuminate,

the strip I82 of low reflectivity. That is, the amplified current is strong enough to move the contact arm of the relay I 91. At that time, the circuit will be so made that the motor I80, which is driven by a battery 200 or other suitable source of power, is rotated in such a direction as to cause the rudder to be so moved as to swing the craft back towards that course where the light spot will again fall wholly on the black line I04. The spring 20I of the other relay I98, which causes rotation of the motor I80 in the opposite direction, has such strength that the contact arm of the relay will close its circuit to the motor when the light spot I85 strikes the motor I80 as required to bring the craft back to and keep it on course. It will be understood that the metal strips I82 and I83 are replaceable by other strips cut in shape to fit the desired course line. Also that line may be straight or curved as desired. J

The electronic devices of the various parts of the apparatus may be made and arranged in ac-,

cordance with standard practice. The photocells of the pilot tube, both inside and out, are to be particularly sensitive to infrared light because of the necessity for picking up a celestial body during a stormy period. For example, I may use an argon gas filled photo emissive tube having a cathode of caesium on caesium oxide applied to a base of silver for activation by the rays from the sun. For a photo voltaic cell, I may use a copper oxide or photronic cell. A resistance cell may be of the selenium type, or I may use a thalofide cell having a platinum disk provided with a coating of thallium metal sensitized by oxygen and sulfur. Molybdenum sulfide is sensitive to infrared and may be employed. Various types of thermocouples may be employed. The

term light as used herein applies to any electromagnetic wave or radiant energy derived from a celestial body and particularly the light within the range of the infrared and ultraviolet portions of the spectrum which will serve to maintain the required fix.

Operation If it is desired to fly east from-a point near Philadelphia, Pa., located at 40 N. latitude 75 W. longitude, to a point near Cape Town, South Africa, located at S. latitude and 19 E. longitude, as represented by the points P and S on Fig. 2, it is merely necessary to plot accurately on the chart the exact positions of the two end points or at least the destination, and then draw the line I04 between these points. That line may be straight to represent a rhumb line course or it may be curved, such as is shown at the lower portion of line I04, if it is desired to fly in a given path or to avoid storm centers or local weather conditions or to go around cities or other locations. The two metal strips I82 and I83 have their edges cut to conform with the plotted course and they are removably fastened on the chart.

If the compass 26 is a magnetic north seeking compass and does not point to the true North Pole, then mathematical corrections may be made on the chart for this and other errors, as is known by navigators. All corrections are made in the plotted curve I04 and not in the mechanism or its controls. Even if the compass does not hold the axis of shaft I2 in a true north and south plane, yet the electronic pick-up mechanism will move the pilot tube to maintain its celestial fix inspite of any deviation of the magnetic pole from the true North Pole. The navigator merely plots the curve to make an accurate correction for this deviation at the point of destination.

It is, however, desirable that the gyrosyn compass 26 be capable of holding the supporting 1 frame in an accurate position irrespective of variations in the craft movement. While various constructions may be employed, I prefer to use a Sperry "gyrosyn self-synchronizing gyroscopic compass which includes a horizontal flux valve that detects magnetic lines of force of the earth's field and is arranged to seek the magnetic north and south. The direction sensed by the compass is transmitted electrically through a power amplifier to the servomotor 24. The high speed gyro is the rotor of a 3-phase induction motor. and a variable transformer pick-oil detects angular movements of the turntable 23 and responds to stabilize and hold the turntable correctly oriented in spite of craft movements.

It is also feasible to swivel the frame It relative to the supporting rod I9, so that the frame will hold the shaft I2 in a true north and south plane, and thus correct for the magnetic deviation at the destination point. Since it is merely desired to reach a given point on the earths surface, it is immaterial as to whether the charted course is properly plotted or what may be its shape, providing the destination is accurately plotted.

The pilot tube moves automatically under the control of the electronic pick-up mechanism to point it directly at the celestial body. Hence, it is not necessary that the latitude of the starting point be known. If the longitude or the differangular reading and the difierential Selsyn I62 agrees therewith at the time of starting. The navigator sets the courser I05 so that the light spot I falls exactly at P on the course I04.

This is done by loosening the set screws I21 (Figs. 2 and 9) and I13 (Fig. 5) and adjusting the position of the courser without rotating drums I24 and I09 that control the position of the courser thereafter.

The longitude need not be known, since the courser may be set correctly at the starting point P and the clock I60 may be so adjusted as to give a zero reading on the diflerential Selsyn. This 24 hour clock I60 drives the rotor IIiI of its associated Selsyn at the angular rate of rotation of the earth. Hence, if the craft is standing still, the differential Selsyn will maintain a zero reading; but when the craft moves to the east, the pilot tube swings to the west at a faster angular rate than that of the clock Selsyn rotor. The directions of rotation of two rotors of the clock Selsyn and the longitude Selsyn are considered as algebraically opposite in sign, so that if they both rotate through 45 inthe same direction, their sum of +45 and 45 is zero, or the craft has not moved.

If during a trip, the clock Selsyn shows a total angular movement of or an elapsed six hours of time, and the longitude Selsyn has made an angular movement of 45 in the same direction, the algebraic sumof these angles is 45 which shows that the craft has moved 45 west. If the clock movement was 45 and the longitude Selsyn moved in the same direction, this indicates an easterly travel of 90. Similarly, the southerly variation of latitude causes the pilot tube to swing higher towards the zenith and thus rotates the latitude Selsyn and so'causes the courser I05 to move in a southerly direction over the chart.

If the courser is exactly on the black line I04, then the craft rudder is not actuated by the motor I80 (Fig. 14) but if there is any deviation from that course line by the light spot I85, then the I back toward the plotted course. Hence this apparatus is fully automatic for guiding the craft to the destination point plotted on the chart.

Various modifications may be made of this construction within the scope of this invention. and the above disclosure is to be interpreted as setting forth the principles and my preferred embodiments thereof without imposing limitations on the appendant claims.

I claim: a

1. A navigating instrument for craft comprising a light seeking electronic device which is automatically controlled by radiant energy directed from and movable to maintain a fix on a celestial body during the craft movement, a stationary chart remote therefrom, a course follower moyable over said chart, and means controlled by a variation in movement of said device as it maintains the celestial fix which moves the course follower relative to the chart in accordance with the craft movement.

2. A navigating instrument for craft com,- prising a light seeking electronic device which is automatically controlled by radiant energy directed from and movable to maintain a fix on a celestial body during the craft movement, a chart having a surface in one plane on which the'latitude and longitude angles of points on a course are plotted in rectangular coordinates, a course follower movable over saidchart, and means controlled by a variation in movement of said device caused by the craft movement as the celestial fix is maintained which moves the course follower relative to the charted course in accorda nce with the craft movement.

3. A navigating instrument for craft comprising a movable light seeking electronic device which automatically maintains alignment with a light ray from a celestial body, a chart remote therefrom having a surface in one plane on which the latitude and longitude angles of a course are plotted in rectangular coordinates on a noncritical scale, a course follower mounted to move over the chart and electrical apparatus controlled by a variation in movement of said device between stationary and movable craft conditions which moves the course follower relative to the charted course in accordance with the craft movement.

4. A navigating instrument for craft having rudder control apparatus comprising a movable electronic light seeking device which automatically maintains a fix on a celestial body, a stationa'ry chart remote from and independent of said device on which a destination is plotted on on the chart in'lin' r measurements that are multiples of the angular latitude and longitude changes of craft position.

6. A navigating instrument for a craft having rudder control apparatus comprising a chart having a surface in one plane on which the latitude and longitude angles of a course are plotted in-rectangular coordinates of a noncritical scale, an electronic light seeking device which automatically maintains a fix on a celestial body, means controlled by the variation in movement of said device between stationary and moving craft conditions which indicates an instantaneous craftposition on the chart and means goverened by a variation in the charted craft position from the plotted course which governs the rudder control apparatus and causes the craft to bear towards the plotted course.

7. A navigating instrument for a craft having rudder control apparatus comprising a flat chart having latitude and longitude angles voi? a course plotted in rectangular coordinates on a selected scale, an electronic light seeking device which automatically maintains a celestial fix and moves through angles determined by variations in the crafts latitude and longitude, a course f ollower movable over the chart, means for translating variations in the angular movements of said device as linear movements of the course follower and moving the follower over the chart to give an instantaneous indication of craft position, and means governed by a departure of the follower from the plotted course which causes the rudder control apparatus to steer the craft towards the required course.

8. A navigating instrument for craft comprising an angularly movable electronic light seeking device, a universal support therefor, means governed by the device for moving it angularly in an east-west direction and to maintain a celestial fix, a chronometer driven member independent of said device and support which is rotatable in angular synchronism with the earth, and a differential mechanism controlled by a variation between the angular east-west movement of said device and the angular movement of said member which responds to a change in longitude of the craft.

9. A navigating instrument for craft according to claim 8 comprising a chart having a course plotted thereon, a course follower movable over the chart, and means governed by said difierential mechanism for moving the course follower in a non-critical scale, a course follower movable over the chart, means controlled by variations in movement of said device in response to a directional movement of the craft which causes the course follower to move over the chart in accordance with the instantaneous craft position and apparatus controlledby the movement of said follower relative to the destination which governs the rudder control apparatus.

' 5. A navigating instrument for craft comprising a movable electronic light seeking device which automatically maintains a fix on a celestial body, a chart having a surface in one plane on which the latitude and longitude angles of points on a course are plotted in rectangular coordinates on a non-critical scale. and means controlled by a deviation in movement of said device caused by the craft movement as the celestial fix is maintained for indicatingwhe craft movement response to a variation in longitude of the craft.

10. A navigating instrument according to claim 8 for craft having rudder control apparatus comprising a chart having a course plotted thereon, acourse follower movable relative to said plotted course, means governed-by said differential mechanism for moving the follower in response-to a variation in longitude of the craft and mechanism responding to a deviation of the course follower,

from the plotted course which controls said apparatus.

11. A- navigating instrument for craft comprising; an electronic device activated by light directed from a celestial body, an equatorial mount therefor having a rotatable shaft, a support to tilt the shaft in a vertical plane and an angularly adjustable arm carrying the device which'is adjustable for declination and is swung by rotation. of the shaft about the shaft axis, means to hold the shaft in a north and south plane, motors governed by the device which rotate and swing the shaft and move the device to aceame maintain a fix on said celestial body as the craft moves, an independent chronometer which rotates at the angular rate of earth rotation, a synchronized generator and motor set governed by variations in the angular tilted position of the shaft and arm caused by the craft movement which respond to latitude changes, differential mechanism responding to a variation in the angular rates of rotation of the shaft and the chronometer, a chart having a plotted course which is remote from said device, and means governed by said set and differential mechanism which indicates the craft position on the chart relative to the plotted course.

12. A navigating instrument according to claim 11 comprising a latitude Selsyn generator and motor set connected to synchronize with the angular tilting movement of the rotatable shaft and means governed by said set which responds to a change in latitude of the craft position and the resultant tilting movement of said shaft.

13. A navigating instrument according to claim 11 comprising a longitude Selsyn generator having a rotor responding to an angular swinging movement of the arm about the shaft axis as the 18 corresponding with the craft position and an electronic device responsive to the light spot departing from the plotted course which causes the rudder control apparatus to guide the craft towards the intended course.

17. A navigating instrument for a craft comprising a universally mounted light activated pick vup device which is automatically controlled by simultaneously with the angular movement of fix is maintained, a chronometer driven Selsyn rotor synchronized with the earth rotation, and a difierential Selsyn controlled by said Selsyn generators which responds to a difference in angularity between the rotors of said generators as the longitude of the craft is changed.

14. A navigating instrument for craft comprising an angularly movable electronic light seeking device, a universal support therefor motor driven mechanism governed by the device which causes the latter to maintain a celestial fix, a stationary chart remote from the device and its support which has a surface in one plane on which is plotted a course to a destination in latitude and longitude coordinates on a noncritical scale, means for moving a light spot relative to the plotted course in response to angular movements of the device so that the light spot indicates the craft position according to the scale of the chart and an electronic device responsive to a deviation of the light spot to one side of the plotted course.

15. A navigating instrument for craft comprising an angularly movable electronic light seeking device, means governed by the device for moving it to maintain a celestial fix, a remote chart having a surface in one plane on which the latitude and longitude of points on a course are plotted in rectangular coordinates, a course follower providing a spot of light which is movable over the chart, means for moving the follower and light spot in response to angular movements of the device caused by a change in latitude and longitude of the craft, light reflective surfaces defining the plotted course and electronic control apparatus which is governed by a deviation of the light spot from the plotted course onto one of said surfaces.

16. A navigating instrument for craft having rudder controlapparatus comprising an angularly movable electronic light seeking device and associated mechanism to maintain a celestial fix, a stationary chart remote from the device having a surface in one plane on which the latitude and longitude of points of a course are plotted in rectangular coordinates. a course follower providing a light spot on the chart, means governed by angular movements of the device caused by variations in craft latitude and longitude which moves the light spot to a position on the chart said device and to be positioned according to the instantaneous craft position.

18. A navigating instrument for a craft comprising an electronic device which is activated by direct light from a celestial body, means including an equatorial mount having a rotatable shaft carrying the device and a tiltable support for the shaft whereby the axis of the shaft may be tilted in a north and south plane, mechanism governed by activation of said device which rotates and tilts the shaft to maintain a fix on said body as the latitude of the craft changes, a stationary chart remote from said mount on which a course is plotted, a course follower movable over the chart, and a synchronized electrical generator and motor mechanism connecting said follower and tiltable support so that the follower moves over the chart as the shaft axis is tilted according to a latitude variation of craft position.

19. A navigating instrument according to claim 18 comprising an independent chronometer mechanism which rotates at the angular rate of the earth rotation, two synchronized generator and motor. sets connected respectively to the chronometer mechanism and the shaft, a differential mechanism governed by said synchronized sets which responds to the angular differences therebetween, and means whereby the differential mechanism causes the course follower to move over the chart according to a variation in longitude.

20. A navigating instrument for a craft according to claim 11 comprising a course follower governed by the differential mechanism and the generator motor set which is movable over the chart ina definite relationship to the angular movement of the light activated device and means on the follower which indicates the craft position relative to the course on the chart.

21. A navigating instrument according to claim -11 for a craft having a motor driven rudder control apparatus comprising mechanism governed by a deviation of the indicated craft position from the plotted'course which causes said apparatus to steer the craft towards the charted course.

' ROBERT J. HERBOLD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

